The only thing possible could be the "Bradley Effect" on those polled. This is excluding down right skulduggery. They do not wish to be seen in a bad light by the pollster and give out what the pollster is thought to believe. The Bradley Effect is one name for that.
Akin still survives being thrown under the bus. (imho) It has been noted that the MSM seems to have forgotten Travon Martin- George Zimmerman.
A correction to my post on the Bradley Effect. It is usually in the case of a black candidate against a white candidate. The person polled not wishing to appear “racist”. It can be applied also to a person not wishing to displease the pollster.